[docs] Fix download links to addons builds

Author: zpao

docs/downloads.md

@@ -28,14 +28,14 @@ The uncompressed, development version of React core with inline documentation.
 <script src="http://fb.me/react-{{site.react_version}}.js"></script>
 ```
 
-#### <a href="http://fb.me/react-{{site.react_version}}.min.js">React With Add-Ons {{site.react_version}} (production)</a>
+#### <a href="http://fb.me/react-with-addons-{{site.react_version}}.min.js">React With Add-Ons {{site.react_version}} (production)</a>
 The compressed, production version of React with [add-ons](/react/docs/addons.html).
 
 ```html
 <script src="http://fb.me/react-with-addons-{{site.react_version}}.min.js"></script>
 ```
 
-#### <a href="http://fb.me/react-{{site.react_version}}.js">React With Add-Ons {{site.react_version}} (development)</a>
+#### <a href="http://fb.me/react-with-addons-{{site.react_version}}.js">React With Add-Ons {{site.react_version}} (development)</a>
 The uncompressed, development version of React with [add-ons](/react/docs/addons.html).
 
 ```html